U.S. patent number 6,333,004 [Application Number 09/479,959] was granted by the patent office on 2001-12-25 for apparatus and method for removing microbial contaminants from a flowing fluid.
Invention is credited to Dan M. Sheldon.
United States Patent |
6,333,004 |
Sheldon |
December 25, 2001 |
Apparatus and method for removing microbial contaminants from a
flowing fluid
Abstract
A cell culture incubator comprising a chamber, an airflow
passage through which fluids may recirculate through the chamber, a
filter disposed within the airflow passage, and a structural
component constructed of a material with anti-microbial properties.
The structural component is disposed in the airflow passage so that
microbial contaminants in air flowing into or within the incubator
will contact the anti-microbial structural component and be
retained in a portion of the airflow passage. The portion of the
airflow passage in which the microbial contaminants are retained
may be adjacent to the structural element.
Inventors: |
Sheldon; Dan M. (Newberg,
OR) |
Family
ID: |
23906121 |
Appl.
No.: |
09/479,959 |
Filed: |
January 10, 2000 |
Current U.S.
Class: |
422/4; 422/122;
435/303.1; 435/809 |
Current CPC
Class: |
A61L
2/238 (20130101); A61L 9/16 (20130101); C12M
37/00 (20130101); C12M 37/02 (20130101); C12M
41/14 (20130101); Y10S 435/809 (20130101) |
Current International
Class: |
A61L
2/16 (20060101); A61L 2/238 (20060101); A61L
9/16 (20060101); C12M 3/06 (20060101); A61L
009/00 (); B01L 001/00 () |
Field of
Search: |
;435/266,289.1,303.1,809
;422/4,122,123,104 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
8-71340-A |
|
Aug 1996 |
|
JP |
|
10-234351-A |
|
Oct 1998 |
|
JP |
|
Other References
"Waterjacketed CO.sub.2 Incubators, Models 1815TC, 1825TC, 1845TC,
Sheldon Manufacturing, Inc.," Mar. 1990. .
Lucille A. Ouellette, "Control and Prevention of Contamination in
Cell Culture Incubators," date unknown. .
Full Size Water-Jacketed Incubators, Ultima and Elite Series, Revco
Catalogue, www.revco-sci.com, Oct. 19, 1999. .
"Waterjacketed CO.sub.2 Incubators, Models 1815TC, 1825TC, 1845TC,
Installation and Operating Instructions," Sep. 15, 1988..
|
Primary Examiner: Beisner; William H.
Attorney, Agent or Firm: Kolisch Hartwell Dickinson
McCormack & Heuser
Claims
What is claimed is:
1. A cell culture incubator, comprising:
a chamber;
an airflow passage through which gasses may recirculate in and out
of the chamber;
a filter disposed within the airflow passage, the filter having a
filter element;
and a structural component constructed of a material with
anti-microbial properties, wherein the structural component is
disposed within the filter upstream of the filter element so that
microbial contaminants in air flowing into the incubator will
contact the structural component and then be retained in the filter
element.
2. The incubator of claim 1 wherein the structural component is
made of copper.
3. The incubator of claim 1, wherein the filter includes a casing,
and wherein the structural component is disposed inside the
casing.
4. The incubator of claim 1, wherein the structural component is a
mesh.
5. The incubator of claim 1, wherein the material with
anti-microbial properties may react with chemical compounds in the
air to form products with anti-microbial properties.
6. The incubator of claim 5, wherein the material with
anti-microbial properties is copper, wherein the chemical compounds
in the air include sulfur oxides, and wherein the products with
anti-microbial properties include copper sulfate.
7. The incubator of claim 5, wherein the material with
anti-microbial properties is copper, wherein the chemical compounds
in the air include oxygen, and wherein the products with
anti-microbial properties include copper oxides.
8. An incubator including a chamber, an airflow passage for
recirculating a gas into and out of the chamber, and a filter
configured to filter air circulated through the airflow passage,
the filter comprising:
a casing, the casing defining a passage for airflow through the
filter;
a filter element disposed in the casing such that air must flow
through the filter element to flow through the passage; and
a structural element made of a material with anti-microbial
properties disposed in the casing upstream of the filter
element.
9. The filter of claim 8, wherein the structural component is a
mesh.
10. The filter of claim 8, wherein the material with anti-microbial
properties is copper.
11. The filter of claim 8, wherein the material with anti-microbial
properties may react with chemical compounds in the air to form
products with anti-microbial properties.
12. The filter of claim 11, wherein the material with
anti-microbial properties is copper, wherein the chemical compounds
in the air include sulfur oxides, and wherein the products with
anti-microbial properties include copper sulfate.
13. The filter of claim 11, wherein the material with
anti-microbial properties is copper, wherein the chemical compounds
in the air include oxygen, and wherein the products with
anti-microbial properties include copper oxides.
14. A method of removing microbial contaminants from an incubator
chamber, comprising:
providing an air filter having a structural component made of a
material with anti-microbial properties, the air filter also
including a filter element;
creating an airflow though the filter element;
exposing microbial contaminants in air flowing through the filter
element to the structural component made of a material with
anti-microbial properties; and
trapping microbial contaminants in the filter element after
exposing the microbial contaminants to the structural
component.
15. The method of claim 14, wherein providing a structural
component made of a material with anti-microbial properties
includes providing a mesh made of a material with anti-microbial
properties.
16. The method of claim 14, wherein providing a structural
component made of a material with anti-microbial properties
includes providing a structural component made of a material that
may react with chemical compounds in air to form products with
anti-microbial properties.
17. The method of claim 16, further comprising exposing the
structural element to air before exposing microbial contaminants in
the air to the structural component so that the structural
component reacts with chemical compounds in the air to form
products with anti-microbial properties.
18. The method of claim 17, wherein the material that may react
with chemical compounds in air is copper, wherein the chemical
compounds in air include sulfur oxides, and wherein the products
include copper sulfate.
19. The method of claim 17, wherein the material that may react
with chemical compounds in air is copper, wherein the chemical
compounds in air include oxygen, and wherein the products include
copper oxides.
20. A cell culture incubator, comprising:
a chamber;
an airflow passage; and
a filter configured to filter air circulated through the airflow
passage, wherein the filter includes an inlet, an outlet, an
anti-microbial structural component disposed between the inlet and
the outlet, and a filter element configured to trap microbial
contaminants exposed to the anti-microbial structural
component.
21. The cell culture incubator of claim 20, wherein the filter
element is disposed downstream of the anti-microbial structural
component.
22. The structural component of claim 20, wherein the material with
anti-microbial properties is copper.
23. The structural component of claim 20, wherein the material with
anti-microbial properties may react with chemical compounds in the
air to form products with anti-microbial properties.
24. The structural component of claim 23, wherein the material with
anti-microbial properties is copper, wherein the chemical compounds
in the air include sulfur oxides, and wherein the products with
anti-microbial properties include copper sulfate.
25. The structural component of claim 23, wherein the material with
anti-microbial properties is copper, wherein the chemical compounds
in the air include oxygen, and wherein the products with
anti-microbial properties include copper oxides.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an air filter that includes a
structural component made of a material with anti-microbial
properties. More particularly, the invention relates to an air
intake filter for a cell culture incubator that includes a
structural component that inhibits the reproduction of microbial
contaminants and traps them away from the chamber of the
incubator.
The use of cell cultures is a tremendously popular research tool in
a variety of scientific disciplines. It involves the in vitro
growth of cells in a cell culture incubator, for example a
humidified CO.sub.2 incubator. The popularity of the technique has
lead to many advances in cell growth techniques and equipment,
which have made the growth of cell cultures more reliable and
reproducible. However, some problems associated with cell culture
exist despite the many recent advances made in the field. One of
the most prevalent of these problems is contamination.
Many sources exist for the contamination of cell cultures. For
example, any piece of equipment that a cell culture may encounter,
such as an autoclave, fume hood or incubator, may introduce
contaminants into the culture. Humidified CO.sub.2 cell culture
incubators are designed to provide a suitable environment for the
growth of cells in culture. The primary functional components of
these incubators include a chamber in which the cultures are placed
for growth, a blower to circulate air in the chamber, a heating
system to heat the chamber to an optimal cell growth temperature,
and a filter to remove particulate contaminants from the chamber.
Additionally, some incubators may include a water pan in the bottom
of the chamber to humidify the cell growth environment or a
CO.sub.2 input system to vary the makeup of the atmosphere inside
the incubator. The resulting warm, moist and dark environment is
perfect for the growth of cell cultures. It is also perfect for the
growth of bacteria, mold, yeast and fungi contaminants.
Contamination can cause several types of problems in a cell culture
incubator. For example, if contaminants infect a cell culture, it
may ruin the culture and any experiment relying on that culture.
Also, contaminants may grow in the humidity pan. The relative
humidity inside an incubator is a function of the evaporation rate
of water from the humidity pan. The rate of evaporation is
dependent upon the surface area of the pan and the surface tension
of the liquid in the pan. If contaminants grow in the pan, they can
alter the surface tension of the water and upset the humidity
characteristics of the chamber.
To prevent the contamination of a cell culture incubator, the
incubator must be cleaned at regular intervals using a rigorous
procedure. Even with regular cleaning, however, some locations in
the incubator are particularly susceptible to contamination. One of
these is the air filter. The air filter in an incubator is
generally mounted on an interior surface of the chamber. The blower
draws air through the filter, where the air is cleaned of
particulate contaminants. Upon leaving the filter, the air flows
through a conduit back into the incubator chamber, and is again
cycled through the filter. One source of the contaminants removed
by the filter is the opening of the chamber door by laboratory
personnel. Microbial contaminants, such as bacteria and spores,
enter the incubator chamber with each opening of the door. These
contaminants are then drawn into the filter by the circulating air
and trapped. They may then grow in the filter. Once the filter is
contaminated, the potential exists for samples in the chamber to be
contaminated as well.
Antibiotics may be added to cell cultures to prevent the
contamination of a sample by a contaminated incubator, but they are
generally not recommended for use in samples, with limited
exceptions. Most antibiotics do not kill the bacteria, but only
slow its growth, and thus do not remove the contaminant from the
chamber. Also, the long-term use of antibiotics may alter the
cultures grown in the incubator, resulting in the selective growth
of antibiotic-resistant strains of cells over non-resistant
strains. Furthermore, the antibiotic may be toxic to the cultured
cells as well. For these reasons, it is not desirable to use an
antibiotic in the cell culture to control contamination.
Some materials are known to inhibit the growth of bacteria and
other microbial contaminants while showing no toxicity toward
eukaryotic cells that are commonly cultured in incubators. Copper
and some of its salts and oxides are among these materials. Copper
compounds have long been used to control such organisms as algae,
mollusks, fungi, and bacteria. Copper sulfate, for example, has
many uses in agriculture. It finds its primary use in the control
of fungal diseases of plants, but is also used against crop storage
rots, for the control and prevention of certain animal diseases
such as foot rot, and for the correction of copper deficiency in
soils and animals. It also has anti-microbial uses outside of
agriculture. For instance, it may be added to reservoirs to prevent
the development of algae in potable water supplies. Copper sulfate,
however, is not the only copper compound with antifungal and
antibacterial applications. Other copper compounds, such as cuprous
oxide (Cu.sub.2 O) and copper acetate (CuCH.sub.2 COOH), have also
been used as fungicides. Despite its heavy use in agriculture and
industry, however, neither copper nor most of its compounds
commonly used in these applications have ever been shown to be
toxic or to cause any occupational diseases.
Incubators have been constructed with copper chambers in the past
to take advantage of the anti-microbial properties of copper
compounds. For instance, Revco currently manufactures an incubator
with a copper bonded interior surface, the Revco ULTIMA incubator,
described in their online catalog at the following website:
http://www.revco-sci.com/catalog/incubators/ultima elite.htm.
It is also available through Fisher Scientific (1994 Fischer
Scientific Catalog, p. 1109). The bonded copper interior surface is
effective to inhibit the growth of many contaminants. However,
contaminants that enter the chamber when the door is opened may
still grow in areas not protected by the copper surface, such as
the blower, the filter or other components. Moreover, if the filter
becomes infected, the blower can spread contaminants from the
filter to all other parts of the chamber. The possibility thus
exists that some of these contaminants which have grown in the
filter and not encountered the copper interior surface may infect
cultures in the chamber.
Thus, problems exist both in inhibiting the growth of microbial
contaminants in the filter of a cell culture incubator, and in
segregating and retaining the inhibited contaminants away from the
chamber.
SUMMARY OF THE INVENTION
One aspect of the present invention provides a cell culture
incubator comprising a chamber, an airflow passage through which
fluids may recirculate through the chamber, a filter disposed
within the airflow passage, and a structural component constructed
of a material with anti-microbial properties. The structural
component is disposed in the airflow passage so that microbial
contaminants in air flowing into or within the incubator will
contact the anti-microbial structural component and be retained in
a portion of the airflow passage. The portion of the airflow
passage in which the microbial contaminants are retained may be
adjacent to the structural element.
Another aspect of the present invention provides an air filter for
removing microbial contaminants from air, comprising a casing, a
filter element, and a structural element made of a material with
anti-microbial properties. The casing defines a passage for airflow
through the filter. The filter element is disposed in the casing
such that air must flow through the filter element to flow through
the passage. The structural element made of a material with
anti-microbial properties is disposed in the casing such that air
must flow through the structural element before flowing into the
incubator.
Another aspect of the present invention provides an anti-microbial
structural element for use in an air intake filter, where the air
filter includes a filter element. The structural component
comprises a mesh of a material with anti-microbial properties,
wherein the mesh may be configured such that all air flowing
through the filter element must pass through the mesh.
Yet another aspect of the present invention provides a method of
removing microbial contaminants from air, comprising (1) providing
a structural component made of a material with anti-microbial
properties in an air filter, the air filter including a filter
element, wherein the structural component is located at a point
upstream or downstream of the filter element; (2) creating an
airflow though the filter element; (3) exposing microbial
contaminants in air flowing through the filter element to the
structural component made of a material with anti-microbial
properties; and (4) trapping microbial contaminants in the filter
element after exposing them to the structural component made of a
material with anti-microbial properties. Referring to (3), the
structural component may take the form of a device capable of
killing microbial contaminants. That device could be an electrified
gradient of wires or other elements, a microwave emission source,
or other radiation-emitting devices.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a filter according to a first
embodiment of the present invention.
FIG. 2 is a top plan view of the filter of the embodiment of FIG.
1.
FIG. 3 is a top plan view of the filter of the embodiment of FIG. 1
with the top piece removed.
FIG. 4 is an isometric view of an anti-microbial mesh according to
the first embodiment of the present invention.
FIG. 5 is a sectional view taken along line 5--5 of FIG. 4.
FIG. 6 is a sectional view of an incubator showing airflow through
a filter according to the present invention.
FIG. 7 is a flow diagram depicting a method of removing microbial
contaminants from a flowing gas according to an embodiment of the
present invention.
FIG. 8 is a flow diagram depicting a method of removing microbial
contaminants from a flowing gas according to another embodiment of
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides an apparatus and a method for
removing microbial contaminants from a flowing fluid. The method is
particularly suited for application in a cell culture incubator.
FIG. 1 shows generally a schematic of an apparatus that may be used
to practice the present invention. A filter is indicated at 10. The
filter has an upper piece 12 and a lower piece 14. Upper piece 12
defines a hole in its center portion, while lower piece 14 is
solid, as shown in FIG. 2, forcing air to flow out of filter 10
through the hole in upper piece 12. A filter element 16 is disposed
between the upper piece and lower piece. The filter element is held
in place by a mesh 18 surrounding the filter element on one side
and a bracket 20 on the other side. Airflow, indicated at 22 and
24, passes through filter 10 by first passing through mesh 18,
through filter element 16, and out of the hole defined by top piece
12. Top piece 12 and bottom piece 14 are joined together by mesh
18, with one edge of mesh 18 bonded to top piece 12 and the other
to bottom piece 14.
FIG. 3 shows a view of the top of filter 10 with top piece 12
removed. Filter element 16 can be seen in this view to be
configured in a zig-zag pattern to maximize its surface area. This
maximizes the speed of airflow through the filter because the total
surface area of the pores for air to pass through is maximized.
This also maximizes the life of the filter, as a larger surface
area will clog with particulate less quickly than a smaller surface
area.
According to the present invention, one of the structural
components of an embodiment of the invention is constructed of a
material with anti-microbial properties. While many materials, both
solid and liquid, may be used for the structural component of the
present invention, copper is a preferred material. When elemental
copper metal is exposed to air, it reacts with various chemical
compounds present in the air to form a variety of copper salts and
oxides. For instance, in the presence of sulfur oxides, copper will
form copper sulfide. In the presence of oxygen, the copper will
oxidize over a period of time to Cu.sub.2 O and CuO. These
compounds will generally form as a surface layer on the elemental
copper metal. Additionally, water-soluble copper compounds such as
copper sulfate may exist as an aqueous phase if there is any water
present on the surface of the copper. Both a surface layer and an
aqueous layer of the anti-microbial copper compounds will be
present on any copper in the warm, moist environment of the
incubator interior. The presence of these compounds on the surface
of a structural element made of copper will prevent bacteria,
fungi, algae, and other contaminants from growing on the
element.
In one embodiment of this invention, mesh 18 may be made of copper.
Mesh 18 is shown separate from the rest of filter 10 in FIG. 4.
Mesh 18 includes both vertical members 26 and horizontal members
28. Mesh 18 is configured to completely surround filter element 16
with no gaps. Thus, according to the embodiment of the invention
shown in FIG. 1, mesh 18 will be the cylindrical shape shown in
FIG. 4. The size of the gaps defined by vertical members 26 and
horizontal members 28 may be chosen to suit any particular filter
or chamber design to accommodate particular airflow
characteristics.
FIG. 5 shows a sectional view of the mesh taken along line 5--5 of
FIG. 4. Though FIG. 5 demonstrates the surface condition of a mesh
in a humidified incubator environment, the mesh will show
anti-microbial properties in any incubator--humidified or not. The
view is taken as a cross-section slightly off the center of a
vertical member 26, and the horizontal members 28 appear as nodes
along vertical member 26. A thin surface layer 30 covers all
exposed surfaces of mesh 18. Surface layer 30 is a solid layer of
various copper compounds formed in the reactions between copper and
chemicals present in the air inside the incubator chamber. Among
the compounds present in layer 30 will be many of the copper
compounds that exhibit anti-microbial properties. Due to the moist
environment inside the incubator, there may be some moisture 32
present on the surface of mesh 18. Though droplets of moisture 32
are shown only in two places on mesh 18 in FIG. 3 for reasons of
clarity, in reality moisture 32 may be found covering the entire
surface, or any fraction of the surface, of mesh 18. Any
water-soluble copper compounds present in surface layer 30 will be
found as an aqueous phase in moisture 32.
Microbial contaminants encountering surface layer 30 or moisture 32
will be inhibited from proliferating by the compounds present in
layer 30 and moisture 32. Furthermore, moisture 32 may drip down
mesh 18 and into the bottom of the filter, defined by bottom piece
14. Bottom piece 14 is solid, and will hold any moisture that drips
off of mesh 18. The moisture may spread across the surface of
bottom piece 14, and may encounter the bottom edge of filter
element 16. Filter element 16 is often made of a material such as
filter paper that may absorb moisture. Moisture may be drawn up
into filter element 16 from the surface of bottom piece 14 by
capillary action, and impregnate filter element 16 with any aqueous
copper compounds present in moisture 32. The anti-microbial
compounds may spread from mesh 18 to other parts of filter 10,
inhibiting the growth of contaminants throughout filter 10.
Furthermore, any contaminants that are drawn into the filter will
remain in the filter, trapped by filter element 16. The
contaminants will remain in contact with the anti-microbial
compounds present in both mesh 18 and filter element 16, and will
not contaminate the filter. Finally, the contaminants will not fall
out of filter 10 back into the chamber, as the direction of airflow
from the chamber into filter 10 will hold the contaminants inside
of filter 10. In a non-humidified incubator, surface layer 30 of
various copper compounds will still be present, but less moisture
will be present on the surface of mesh 18. In another embodiment of
the present invention, the structural element may take the form of
filter element 16 impregnated with the anti-microbial
compounds.
FIG. 6 depicts the use of filter 10 in an incubator. An incubator
is indicated generally at 34. Incubator 34 includes a casing 36, a
chamber 38, an interior surface 40, a blower 42, an optional water
pan 44, and filter 10. The incubator will also include a heating
unit, which is not depicted in this figure. Arrows 46 indicate the
direction of airflow in the incubator. Air is continuously
circulated through filter 10, out blower 42, through the incubator
casing 36, and back into chamber 40 at the bottom of the chamber,
where it is again drawn upward toward filter 10. When the door to
chamber 40 is opened to insert or remove a sample from chamber 40,
contaminants present in the air, on any tools inserted into the
chamber, or on the laboratory personnel using the incubator may be
introduced into chamber 40. These contaminants may be drawn into
filter 10 by the upward air currents created by blower 42. Upon
entering filter 10, the contaminants will encounter anti-microbial
mesh 18 and filter element 16. Thus, the contaminants will be
trapped in filter element 16 and the copper compounds generated at
mesh 18 will inhibit their reproduction.
Another aspect of the present invention provides a method of
removing microbial contaminants from air. The method is suited for
use in any application where a sterile, microbe-free environment is
desired, such as in humidified CO.sub.2 cell culture incubator. One
embodiment of this aspect is shown in FIG. 7. First, a filter is
provided at 43. According to this embodiment, the filter will have
a structural component made of an anti-microbial material, and will
also have a filter element. Next, a flow of air is created through
the filter at 45. The flow of air will bring any microbial
contaminants present in the air into contact with the
anti-microbial material of the structural component, and will
expose the contaminants to the anti-microbial structural component
at 47. Finally, after exposing the contaminants to the
anti-microbial material, the contaminants are trapped in the filter
element at 48 and thus removed from the airflow. The air downstream
of the filter will be contaminant free.
Another embodiment of this aspect of the present invention is shown
in FIG. 8, which illustrates the removal of microbial contaminants
from the air in a cell culture incubator. In this application, a
copper mesh is provided in a cell culture incubator filter in a
location upstream of the filter element at 50. Next, a flow of air
is created through the filter at 52. The airflow can be created by
a blower, or by any suitable pumping method. Exposure of the mesh
to the warm, moist, CO.sub.2 rich air inside the incubator will
result at 54 in the formation of different copper compounds, such
as CuSO.sub.4 and Cu.sub.2 O, that may display anti-microbial
properties. Any microbial contaminants in the incubator will be
drawn into the filter and exposed to the copper compounds at 56.
Finally, the microbial contaminants will be trapped in the filter
element at 58, where they will be prevented from reproducing by the
presence of the copper compounds.
While the invention has been disclosed in its preferred form, the
specific embodiments thereof as disclosed and illustrated herein
are not to be considered in a limiting sense as numerous variations
are possible. Applicants regard the subject matter of their
invention to include all novel and non-obvious combinations and
subcombinations of the various elements, features, functions and/or
properties disclosed herein. No single feature, function, element
or property of the disclosed embodiments is essential to all
embodiments. The following claims define certain combinations and
subcombinations which are regarded as novel and non-obvious. Other
combinations and subcombinations of features, functions, elements
and/or properties may be claimed through amendment of the present
claims or presentation of new claims in this or a related
application. Such claims, whether they are different, broader,
narrower or equal in scope to the original claims, are also
regarded as included within the subject matter of applicants'
invention.
* * * * *
References